android_demo01

 /layout/activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <TextView
         android:id="@+id/mytext"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
        />
    <Button
        android:id="@+id/mybtn"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />

</RelativeLayout>

com.example.demo01textviewbutton.MainActivity
package com.example.demo01textviewbutton;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

//当在/layout/activity_main.xml中加控件后，Ｒ会自动生成相应的资源文件ＩＤ
public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
      //编写相应业务逻辑
        TextView textView = (TextView) super.findViewById(R.id.mytext);
        textView.setText("buy big house");
        Button mybutton=(Button)super.findViewById(R.id.mybtn);
        mybutton.setText("clink me ,xixihehehaha");
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

R.java中生成以下：   
 public static final class id {
        public static final int action_settings=0x7f080002;
        public static final int mybtn=0x7f080001;
        public static final int mytext=0x7f080000;
    }